This invention relates to a sealed blister assembly wherein a plastic sheet and plastic lid are joined together to form an impermeable seal. The seal is formed solely by engagement of an undercut in the plastic sheet and a shoulder in the plastic lid. No adhesives or further backing sheets are required to be used to obtain the seal.
Blister packages have been well known for many years. They have been used for many purposes in different types of packaging applications. In some inexpensive and undemanding applications, items can be packaged in plastic blisters with simple cardboard backing. The blister sheet and backing may or may not be adhered together.
Industries where blister packaging is widely used include packaging of food and pharmaceutical products. These applications are typically more demanding than other applications, because there is the need for a seal between a blister sheet and lid. The seal is required to keep the food and medications fresh and unspoiled. This is accomplished conventionally by a heat seal or adhesive between the blister sheet and lid. There may also be one or more additional backing sheets to form barrier layers or provide more integrity to a package.
Problems with conventional sealed blister package assemblies include the fact that the adhesive or heat sealing process can adversely affect the product being packaged. Also, the system can be very complicated and difficult to assemble. These types of systems are primarily efficient only in high-volume, manufacturing applications.
It is accordingly an object of the present invention to overcome the foregoing drawbacks and provide a sealed blister assembly that does not require an adhesive or heat sealing process to seal a blister sheet and a lidding sheet in order to obtain an impermeable seal.
In one embodiment, a sealed blister assembly includes a plastic sheet and plastic lid. The plastic sheet has a recess formed therein, the recess having a perimeter all around an opening into the recess, and the perimeter further comprising an undercut. The plastic lid is adapted to attach to the perimeter of the recess and cover the opening into the recess. The plastic lid comprises a raised ridge having an outside edge adapted to engage the undercut of the plastic sheet around the entire perimeter. The engagement of the ridge and undercut forms the seal, whereby a sealed blister is formed from the plastic lid and the recess of the plastic sheet. The plastic sheet may comprise a plurality of recesses and the plastic lid comprise a corresponding plurality of ridges to form a plurality of sealed blisters. Further, the outside edge of the ridge may comprise walls that flare outwardly. The undercut may comprise side walls, the outside edge of the ridge may comprise walls, and the sealed blister would thereby result from the engagement of the undercut side walls and ridge walls. The plastic sheet and/or the plastic lid may be comprised of polyethylene. Still further, the undercut side walls may flare outwardly in a corresponding fashion to the flared ridge walls. Also, the undercut side walls may be shorter than the ridge walls. The sealed blister formed may be used for packaging a medication, and the sealed blister meets or exceeds the requirements to be a U.S.P. Class A or Class B individual unit-dose container.
In another embodiment, the invention includes a package assembly for dispensing a pharmaceutical medication. The assembly comprises a plastic sheet having a medication receiving recess formed therein. The plastic sheet has a substantially planer shoulder portion disposed along the peripheral portion of the sheet and further with a perimeter around the recess. The package assembly further comprises a pharmaceutical medication positioned in the recess of the plastic sheet. A plastic lid is positioned in an overlaying relationship to the plastic sheet, the plastic lid comprising a raised ridge having an outside edge corresponding to the perimeter of the recess and frictionally engaging the perimeter to thereby close the recess and seal the medication therein. The perimeter of the recess may further comprise an undercut, and the ridge on the plastic lid frictionally engages the undercut to seal the medication therein. Further, the plastic sheet may comprise a plurality of recesses wherein a pharmaceutical medication is positioned in each recess, and wherein the plastic lid comprises a corresponding plurality of ridges to form a plurality of medication-containing sealed blisters.